A conventional conversation control system outputs a stored reply sentence suitable for the contents of an utterance of a user, based on the contents of the utterance. Specifically, the conversation control system compares the contents of an utterance of a user with a stored phrase group, so as to search a phrase matching the contents of the utterance from the phrase group. Then, a reply sentence associated with the phrase searched by the conversation control system is output. The user receiving the reply sentence from the conversation control system can feel as if he or she had a conversation with another user.
The above conversation control system, however, has a problem that a reply sentence appropriate to the contents of an utterance cannot be output unless a large number of phrases even slightly similar to the contents of the utterance are stored. If developers of the conversation control system store a huge number of phrases even slightly similar to the contents of an utterance and reply sentences associated with the huge number of phrases in the conversation control system, the conversation control system can output a reply sentence appropriate to the contents of the utterance.
However, in order to allow the conversation control system to search a phrase matching the contents of an utterance, the developers have to store an enormous phrase group in the conversation control system. It has therefore been difficult to develop a conversation control system for outputting a reply sentence appropriate to the contents of an utterance.
The present invention has been made in view of the above problems, and has an object of providing a conversation control system and a conversation control method which can identify morphemes constituting input information provided from a user, retrieve a prepared reply sentence associated with the identified morphemes, so as to output the most appropriate reply sentence to respond to the input information of the user, and also can output an appropriate reply sentence even with a reduced number of reply sentences stored.